since you have multiple processors, you can have over 100% utilization. if you google it, there are thousands of examples and explanations out there. optimizing depends on what you are doing. lots of reads? lots of writes? what type of data are you storing. are you noticing performance issues? long db queries?
–
austinAug 20 '12 at 15:58

Some detail on that

If you had iowait, it could show you that the storage you are using is too slow to serve data fast enough for the processors. But since there is no iowait, the storage isn't the one causing load.

Given that you have 4 processors, a load of 1.5 is nothing to worry about at all. In fact, you shouldn't start wondering about load issues until your load is constantly over 5.

A little something about load

Let's use a metaphor for CPU cores. Let's say that each core is a tube. The load average describes the amount of water that needs to go through the tube.

1 tube means that we can handle a load of 1 without any worrying. This means that if you have a lot of water, the load will increase because the tube is not big enough to let all the water through. (water being processes)

So, if you have 4 cores - you can easily handle a load of 4, before having to worry about adding more tubes :)

I hope it makes sense.

Edit: The obvious

If you are serving just 1 user doing very little, your code might be very bad and you should look into optimizing. But if you are having a fairly busy application running, I wouldn't start the red lights.